function mostrar(idLayer)
{
 var capa
 if (document.layers) capa = eval("document." + idLayer);
 if (document.all) capa = eval(idLayer + ".style");
 if (document.getElementById) capa = eval('document.getElementById("' + idLayer + '").style');

 if (capa.display == "none"){
  capa.display = (document.layers) ? "block" : "block" ;
 }else{
  capa.display = (document.layers) ? "block" : "none" ;  
 }
}